Gordon Brown announced his pre-budget report yesterday. The pertinent chapter for our industry is Chapter 7 (pdf, 26 pages). Driving home last night Radio 4 were asking the question ‘what is a zero carbon home?’. The reporter had even rang up DCLG for an answer - a spokesman said “one which was not a net recipient of electricity from the national grid” but it was clear that the reporters were still somewhat confused. We could wait for the Code for Sustainable Housing (due for publication next week, I believe) for the official definition but I believe what follows will be close.
The commonly cited definition of zero carbon development comes from the London Renewables document, ‘Towards Zero Carbon Developments‘ (pdf, 108 pages):
A zero carbon development is one that achieves zero net carbon emissions from energy use on site, on an annual basis.
Excluded in this definition are embodied energy in construction and demolition and transport energy. This is the simplest definition, although arguably not the most ‘green’ option available. A better definition would be:
A zero carbon house is one that approaches net carbon emissions from energy use in construction and on site over the useful life of the building
There are of course a number of issues with this definition, which I don’t believe the industry is quite ready for yet (but should be by 2016).
Firstly, the embodied energy in building materials and items such as PV panels, boilers etc is still not widely quoted. BRE have developed a methodology (
Ecopoints (pdf, 2 pages) which the
Envest tool uses) but uptake has not been widespread as there is no current driver. This would be the perfect opportunity to move this initiative forward.
There are some in the industry who seem to believe this will be included in Gordon’s plans - see this
article regarding timber framed buildings. Some interesting statistics in there (although they come from UK Timber Frame Association (UKTFA) so possibly not totally impartial). I agree entirely with the essence of what they are saying, but I do think this a some way off realising yet.
The second point with my definition above is what is deemed ‘the useful life of the building’. The government in their own capital expenditure projects tend to use 60 years. Our housing legacy in the UK is currently a mixed bag with Victorian terraces outliving sixties council blocks by 50 years or more. Shorter periods of time would render many of the renewables which are currently in vogue unfeasible if the embodied energy is taken into account.
All this is supposition at this point in time - by next week it should all become clear.
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[...] Some reaction has already been issued, TCPA here (they comment on the fact that this applies to housing only at this stage), BBC here (they mention the proposal to bring water use into the Building Regulations), Building here (subscribers only), Guardian here (controversially - “The House Builders Association dismissed the plan as “gesture politics” that threatened to undermine the government plan to build tens of thousands of new homes in the south-east.”), BRE are more optimistic here. As I predicted last week, the definition of zero carbon housing has been clarified as: A zero carbon home is one with ‘zero net emissions of Carbon Dioxide (CO2) from all energy use in the home’. The definition encompasses all energy use in the home (including energy for cooking, TVs, computers and other appliances) rather than just those energy uses that are currently part of building regulations (space heating, hot water, ventilation and some lighting). It means that over a year there are no net carbon emissions resulting from the operation of the dwelling. This could be achieved either through steps taken at the individual dwelling level or through site wide strategies. So it will not be necessary for each dwelling to have its own microgeneration capacity where development level solutions would be more appropriate. [...]